Selection of soft magnetic materials for particle accelerator magnets

Recently, great effort has been put into improving the performance of particle accelerator magnets by selecting materials with appropriate magnetic properties. The chemical composition and the manufacturing process of these materials determine their magnetic properties. This paper deals with a comparative analysis of the electric and magnetic properties of a broad range of electrical steels and correlates these properties to their chemical composition, in order to select the optimum grade of steel for a magnetic core. The tested samples are electrical steels with Si content in the interval (0.446-3.310)% and Al content in the interval (0.0029-1.260)%. The magnetic tests have been performed with the Epstein frame in quasi-static conditions and measurements of the electrical resistivity have been obtained according to IEC standards. The major hysteresis cycles are presented for each material and their shape are related to the chemical composition. The electrical steel of grade M 140-35 S is the most appropriate for this application.